1. Field of the Invention
The present invention relates to smart cards, and more specifically to contactless smart cards and a process for manufacturing the same.
2. Description of Related Art
Contactless smart cards are plastic cards containing an antenna in the form of a metal coil and an electronic module that is electrically connected to the antenna. The module includes a support and connection package containing an electronic chip. Such contactless smart cards are increasingly being manufactured and used.
At the present time, in order to manufacture such smart cards, a metal coil is formed on one side of a solid sheet of plastic and a parallelepipedal electronic module is placed on this sheet to form an additional thickness. A solder material is interposed between the connection pads of the module and the end of the coil. This assembly is sandwiched between two covering sheets of plastic, and portions are hot laminated in order to produce a card. In another manufacturing process, the electronic module has a part that extends into a through-passage in the central sheet and a collar that ends up as an additional thickness facing the sheet and having connection pads soldered to the coil.
It has been observed that such laminating generates tensile forces in the spots of solder so that after laminating, pockets not filled with material remain around the module. This results in weakened electrical connections between the module and the metal coil. Further, these pockets are likely to cause moisture retention to the detriment of the module, the metal coil, and their electrical connections. To avoid such problems, it is necessary to fill the interstices between the module and the central sheet with a suitable fluid resin before the central sheet is sandwiched between the two covering sheets and before the lamination.
The above conventional smart card manufacturing techniques require the use of low temperature bonding adhesives that are not very reliable and require the application of a filling resin in order to overcome the problems of stresses after laminating the sheets and of moisture. As a result, relatively thick cards are obtained due to the additional thickness introduced by the electronic module.
In view of these drawbacks, it is an object of the present invention to overcome the above-mentioned drawbacks and to provide an improved process for manufacturing smart cards.
Another object of the present invention is to provide an improved smart card.
One embodiment of the present invention provides a method for manufacturing a smart card. According to the method, a through-passage is produced in a central sheet. At least one face of the central sheet is provided with at least one metal coil having connection parts, and an electronic chip having electrical connection pads is inserted into the passage. At least some of the electrical connection pads of the chip are soldered to the connection parts of the coil, and the faces of the central sheet are provided with external covering sheets to form a stack of sheets. In a preferred method, the stack of sheets is hot pressed or laminated such that the material of the sheets is flowed and fills the space around the chip.
Another embodiment of the present invention provides a smart card. The smart card includes at least one metal coil having at least two connection parts, an electronic chip connected to the connection parts of the coil, a central sheet having a through-passage and the metal coil on one face, and external covering sheets that grip the central sheet. The electronic chip is placed in the passage in the central sheet. In one preferred embodiment, the central sheet and the covering sheets form a single entity in which the chip and the coil are completely embedded.
Other objects, features, and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration only and various modifications may naturally be performed without deviating from the present invention.